So far electrophysiologic (EP) interventions cannot be performed safely under magnetic resonance (MR) guidance due to the risk of radio frequency (RF) heating. For EP procedures it is necessary to monitor the intracardiac electrocardiogram (IECG) (“mapping”) and/or to stimulate the heart (“pacing”). Both require an electrical connection to electrodes on the catheter tip, which is placed inside the heart. This connection can become resonant at the operating frequency of the MR scanner and thus act as an antenna for the applied RF fields, leading to excessive heating especially at the tips.
The wires, which are connected between the electrodes at the catheter tip (“distal side”) and the connections at the other side (“proximal side”) of the catheter, become resonant if they fulfill the condition
            l      ≈              n        ⁢                  λ          2                      =          n      ⁢                        λ          0                          2          ⁢                                                    ɛ                r                            ⁢                              μ                r                                                          ,
with λ0 denoting the wavelength in vacuum, l the length of the wire, εr and μr the effective relative permittivity and permeability for the common mode. The effective εr and μr depend strongly on the properties of the tissue surrounding the wire. As a consequence it is hardly possible to predict if resonance will occur during an intervention, since the length of wire inside the patient as well as the surrounding of the wire changes continuously. This means that EP catheters have to be made inherently RF-safe.
WO 2005/053555 A1 discloses an electrode catheter for the defibrillation, mapping or ablation of cardiac tissue. Said catheter comprises a terminal on the proximal end of the electrode catheter and one or more sensing and/or treatment electrodes that are situated on or in the vicinity of the distal end of the electrode catheter, in addition to at least one electric conductor, which is used to electrically connect a respective sensing or treatment electrode to the terminal. The electric conductor is composed of carbon and the electrode catheter is configured to be suitable for use as part of magnetic resonance tomography and for connection to electrophysiotherapy equipment. Said catheter comprises at least one defibrillation electrode, or at least one sensing electrode for the recording and evaluation of cardiac tissue potentials, or at least one treatment electrode for delivering high-frequency currents for ablation purposes. However, said carbon is not sufficiently RF-safe for medical applications in the field of MR.